SPL Diamond

REVIEW
Jason Kennedy
Mar 26, 2025

Karl-Heinz Fink has a lot to answer for. Not only has he designed some very impressive loudspeakers over the last few decades for all sorts of brands but he has put Epos back in the limelight where it belongs. He has also influenced a few of my reviewing choices and some actual purchases, the latter are rare things I can assure you. It was he who suggested that the SPL Diamond is a very capable DAC for its asking price and it turns out that once again he’s not wrong.

SPL is one of those rare companies that makes electronics for both the studio and home markets, in fact the vast majority of what the German company makes is for professional use. If you have visited a big studio the chances are that there will have been some SPL compressors, equalisers etc in the racks. They are distinguished by anodised alloy facias but this is not unique to the brand, it does however make them stand out from the flat black and silver front panels found on most pro gear.

Only standalone

The Diamond is SPL’s only standalone D/A converter in what it terms the professional fidelity range, a euphemism for domestic audio. It offers digital inputs of all the usual varieties with four S/PDIF options alongside AES and USB and these are selectable with a front panel knob that is a lot more straightforward than usual. The only omission input wise is of a BNC coaxial option, which are rare things today but offer the best connection for S/PDIF sources that have a matching output.

The analogue outputs of the SPL Diamond DAC are of the usual single ended RCA and balanced XLR varieties. The only unusual features on the back panel are a word clock input which reflects the brand’s professional background, and dip switches to change output from fixed to variable. Another pro feature is the option to have fixed output from one pair of outputs and variable from the other. In a situation where you have active speakers and a headphone amp, the Diamond can control volume via the speakers but let the headphone amp do the attenuation. The one feature that would have been nice is a remote control for changing volume but that isn’t apparently an option.

This is a compact piece of kit in height terms. Without its feet the Diamond is only a little over 4cm thick yet the onboard power supply is based around a toroidal transformer; a very slim example of the art presumably but one that offers linear conversion to DC at an unusually high voltage.

High voltage

The Diamond runs an AKM AK4493 DAC chip which converts PCM with a resolution of 32-bits and up to 768kHz, DSD is supported at up to four times or DSD256. Unusually this converter incorporates a low pass filter in the analogue output stage which SPL dub SLP 120 (Super Low Pass). The figure refers to the brand’s Voltair technology which involves running the converter at 120 Volts, which equates to plus or minus 60V as opposed to the plus or minus 15V found in the majority of DACs. They claim that this results in greater dynamic range, better signal to noise and greater headroom.

There is no lock light on the SPL Diamond DAC but the display shows the sample rate available from the connected source. This is effectively the same thing with knobs on, when there’s no signal source the display is blank. It also shows the selected input but there is no option to change this to reveal output level nor to dim or defeat the display. The Diamond’s toggle switches and selector have a solid feel and relays click when sample rate changes, it looks and feels reliable and built to last and in some ways sounds the same.

Tuned for maximum neutrality

The sound is direct and powerful, it‘s as if it has been tuned for maximum neutrality with no tweaking to make the highs sweeter or the mid more colourful. In every piece of electronics decisions have to be made about components, capacitors of the same value have different characters and those differences may not be measurable, but they are audible. This is particularly true in analogue output stages and hi-fi brands tend to build products with a more obvious character than can be heard with this SPL Diamond DAC.

I suspect that the major influence on the Diamond’s character is the high DC voltage that the circuit runs at, it has a much stronger sound than a lot of DACs, with bass that has real power and weight. I found that this combined better with the USB output of a Melco N10 server/streamer than with the Lumin streamer that is usually placed between it and the DAC. In most instances a direct connection like this results in a soft, dynamically challenged and unengaging sound, here the no-nonsense balance of the DAC perfectly matched the relaxed output of the streaming output on the Melco. With the firmer grip of the Lumin the result was slightly too solid and tight; two yins do not a perfect circle make.

Reflex action

Back with the Melco the results were precise and fluent, the SPL Diamond DAC may seem a little straight laced in balance but this makes all forms of music highly engaging. Even well played review staples like the Locrian Ensemble’s Mendelssohn Octets managed to transcend their aesthetic form and get the musical message across. This recording is very good for assessing instrument tone and three dimensionality of soundstage but all too often these elements can obscure the charm of the music, but not here. Here the tone is not as lavish as it might be but you are drawn into the piece very effectively.

With the electric ‘Non Zero Number’ by The God in Hackney (The World in Air Quotes) the tension in the piece is palpable and when the drums and guitar ramp up the dynamics it gets positively visceral. It was particularly interesting to hear the way in which the drum kit has been limited in the recording, this is not usually so obvious and the fact that the SPL could do this whilst also delivering the power and dynamics was rather a treat.

What word would

I have a Mutec Ref 10 Nano word clock in my armoury and took the opportunity to see what this would bring to the performance of the SPL DAC. What it did was calm down the presentation by reducing low level noise which also opened up the soundstage, the change wasn’t night and day but there was a clear increase in precision and a refinement of the overall result.

It also seemed worthwhile to try out the onboard volume control, even if this meant jumping up and down to get the level right (just like the old days). Here the results were a bit less clear and well defined, as if the leading edges were being blurred and the low level detail becoming masked. That however is in comparison with a Townshend Allegri Reference preamplifier at over four times the price, something was going to give. There wasn’t the sense of compression or loss of scale that often happens with the volume controls included on DACs and streamers so this was a strong result.

The Pachanko effect

Another digital source turned up during the review period that proved to be a rather good partner for the Diamond DAC, this was a Pachanko Labs Constellation Mini server/streamer with a linear power supply and silver SATA cable upgrade (£5,850). This is clearly a fine digital source and one that also worked well here, the DAC delivering some very engaging results with excellent low level resolution. The combo is more precise than the Melco which makes for tremendous insight into familiar pieces of music.

I was particularly taken with the drumming on Esperanza Spalding’s ‘Ebony & Ivy’ (Emily’s D+Evolution), the SPL manages to separate out the various elements but keep them totally coherent and this allows the power of the drums to shine through even though they aren’t high in the mix. The acoustic nature of the instrument gives it a dynamic advantage over the voices and other instruments in the band and this makes it nigh on impossible to keep the air drumming under control.

The SPL Diamond DAC will not be to all tastes. Some will prefer a softer and more relaxed sound. I suspect that it is more real and transparent to the source than many of its peers. If you enjoy the power of good bass it should be very high on your list. Likewise, if you want to be carried away by the sheer brilliance of your favourite music, it warrants more attention than its compact and competitively priced form might suggest.

Technical specifications

Type: Solid-state high-resolution PCM and DSD-capable digital-to-analogue converter/preamplifier.
Digital Inputs: One AES/EBU, two Coaxial, two Toslink, and one USB.
• DSD supported through USB only.
Analogue Outputs: One stereo single-ended (via RCA jacks), one balanced (via XLR connectors). Both outputs are configurable for fixed or variable level operation.
DAC Resolution/Supported Digital Formats: All PCM from 44.1KS/s to 768KS/s with word lengths up to 32-bit, DSD64 (2.8224MHz), DSD128 (5.6448MHz) & DSD256 (11.2MHz). The following format restrictions apply:
• Sample rates above 192kHz are supported through USB only.
• 32-bit word lengths supported through USB only.
Frequency Range: 10Hz – 100kHz (0dBu)
Distortion (THD + Noise): <0.001%, 0dBu, 1kHz
Output Voltage: Not specified.
User Interface: Front panel controls.
Dimensions (HxWxD): 57 x 278 x 300mm
Weight: 3.15kg
Price: £2,500, $2,777, €2,499